From: Maarten Lankhorst <dev@lankhorst.se>
To: intel-xe@lists.freedesktop.org, intel-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org,
Maarten Lankhorst <dev@lankhorst.se>,
Uma Shankar <uma.shankar@intel.com>
Subject: [PATCH 07/10] drm/i915/display: Handle vlv dsi workaround in scanline_in_safe_range too
Date: Thu, 2 Jul 2026 09:21:50 +0200 [thread overview]
Message-ID: <20260702072154.171324-8-dev@lankhorst.se> (raw)
In-Reply-To: <20260702072154.171324-1-dev@lankhorst.se>
Now that we have a macro, might as well handle the VLV dsi workaround
too.
This makes the vblank evasion code slightly more deterministic, by not
looping with interrupts disabled.
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
---
drivers/gpu/drm/i915/display/intel_vblank.c | 36 ++++++++++-----------
1 file changed, 18 insertions(+), 18 deletions(-)
diff --git a/drivers/gpu/drm/i915/display/intel_vblank.c b/drivers/gpu/drm/i915/display/intel_vblank.c
index ca08059e088ea..6f1fa952b5391 100644
--- a/drivers/gpu/drm/i915/display/intel_vblank.c
+++ b/drivers/gpu/drm/i915/display/intel_vblank.c
@@ -739,6 +739,24 @@ static bool scanline_in_safe_range(struct intel_vblank_evade_ctx *evade, int *sc
else
*scanline = __intel_get_crtc_scanline(evade->crtc);
+ /*
+ * On VLV/CHV DSI the scanline counter would appear to
+ * increment approx. 1/3 of a scanline before start of vblank.
+ * The registers still get latched at start of vblank however.
+ * This means we must not write any registers on the first
+ * line of vblank (since not the whole line is actually in
+ * vblank). And unfortunately we can't use the interrupt to
+ * wait here since it will fire too soon. We could use the
+ * frame start interrupt instead since it will fire after the
+ * critical scanline, but that would require more changes
+ * in the interrupt code. So for now we'll just do the nasty
+ * thing and poll for the bad scanline to pass us by.
+ *
+ * FIXME figure out if BXT+ DSI suffers from this as well
+ */
+ if (evade->need_vlv_dsi_wa && *scanline == evade->vblank_start)
+ return false;
+
return *scanline < evade->min || *scanline > evade->max;
}
@@ -769,24 +787,6 @@ int intel_vblank_evade(struct intel_vblank_evade_ctx *evade)
local_irq_disable();
}
- /*
- * On VLV/CHV DSI the scanline counter would appear to
- * increment approx. 1/3 of a scanline before start of vblank.
- * The registers still get latched at start of vblank however.
- * This means we must not write any registers on the first
- * line of vblank (since not the whole line is actually in
- * vblank). And unfortunately we can't use the interrupt to
- * wait here since it will fire too soon. We could use the
- * frame start interrupt instead since it will fire after the
- * critical scanline, but that would require more changes
- * in the interrupt code. So for now we'll just do the nasty
- * thing and poll for the bad scanline to pass us by.
- *
- * FIXME figure out if BXT+ DSI suffers from this as well
- */
- while (evade->need_vlv_dsi_wa && scanline == evade->vblank_start)
- scanline = intel_get_crtc_scanline(crtc);
-
return scanline;
}
--
2.53.0
next prev parent reply other threads:[~2026-07-02 7:21 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-02 7:21 [PATCH 00/10] drm/intel/display: Changes required to make vblank evasion PREEMPT_RT safe Maarten Lankhorst
2026-07-02 7:21 ` [PATCH 01/10] drm/vblank_work: Add methods to schedule vblank_work in 2 stages Maarten Lankhorst
2026-07-02 7:21 ` [PATCH 02/10] drm/vblank: Add a 2-stage version of drm_crtc_arm_vblank_event Maarten Lankhorst
2026-07-02 7:21 ` [PATCH 03/10] drm/intel/display: Make intel_crtc_arm_vblank_event static Maarten Lankhorst
2026-07-10 14:20 ` Ville Syrjälä
2026-07-02 7:21 ` [PATCH 04/10] drm/intel/display: Convert vblank event handling to 2-stage arming Maarten Lankhorst
2026-07-02 7:21 ` [PATCH 05/10] drm/i915/display: Move vblank put until after critical section Maarten Lankhorst
2026-07-02 7:21 ` [PATCH 06/10] drm/i915/display: Remove locking from intel_vblank_evade " Maarten Lankhorst
2026-07-02 7:21 ` Maarten Lankhorst [this message]
2026-07-02 7:21 ` [PATCH 08/10] drm/i915: Use preempt_disable/enable_rt() where recommended Maarten Lankhorst
2026-07-02 7:21 ` [PATCH 09/10] drm/i915/display: Make get_vblank_counter use intel_de_read_fw() Maarten Lankhorst
2026-07-10 14:34 ` Ville Syrjälä
2026-07-02 7:21 ` [PATCH 10/10] drm/i915/display: Do not take uncore lock in i915_get_vblank_counter Maarten Lankhorst
2026-07-10 14:19 ` Ville Syrjälä
2026-07-02 7:56 ` ✗ CI.checkpatch: warning for drm/intel/display: Changes required to make vblank evasion PREEMPT_RT safe Patchwork
2026-07-02 7:58 ` ✓ CI.KUnit: success " Patchwork
2026-07-02 8:33 ` ✓ Xe.CI.BAT: " Patchwork
2026-07-03 2:09 ` ✗ Xe.CI.FULL: failure " Patchwork
2026-07-10 14:43 ` [PATCH 00/10] " Ville Syrjälä
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